The present invention relates to methods and apparatuses for determining the temperature distribution over a surface, using means of the type which do not require physical contact with the surface, and particularly in cases where problems of spatial access do not permit the temperature sensing means to be aimed perpendicular to the surface of interest.
In many fields of technology, it is desired to ascertain the temperature distribution across a surface, to be able to detect the presence and location of hot-spots or other locations where the prevailing temperature deviates from a desired temperature profile. However, as a practical matter, such surfaces may be so located, e.g., behind interfering structures, as to make direct and simple access to such surfaces impossible. For example, it may be desired to ascertain the temperature profile of a very large surface from within a very confined space.
A representative example of this sort of problem is found in coking technology. Each coking chamber in a battery of coking ovens is typically rectangular, has a vertical height on the order of up to 8 meters, a horizontal length on the order to up to 17 meters, but a width on the order of only about 0.4 to 0.5 meters. Accordingly, the interior space of one such coking oven is quite tall, deep and narrow. The temperature profile of, for example, the interior side walls of the coking chamber is of great technological importance, because of the information it yields concerning the uniformity of the coking operation which will occur within the chamber and thereby the quality of the coke to be produced. However, attempts to scan the temperature of the interior side wall of the coking chamber are made very difficult by problems of access. The interior side walls can only be viewed through one of the doors at the two ends of the coking chamber or through a charging opening at the top of the chamber. The direction of view towards the side wall, when looking into the chamber through an end door or charging opening, is of course not at all perpendicular to the surface of the side wall, and indeed will be nearly parallel to the sidewall.
It is well known to ascertain the temperature profile across a surface of interest using so-called infrared T.V. cameras operative for producing heat images. However, when infrared T.V. cameras are employed, it is necessary that the optical axis of the camera be oriented generally perpendicular to the surface of interest, and of course at a great enough distance from the surface of interest when the latter is very large. This is necessary, in order that the field of view of the infrared temperature-detecting camera actually capture the surface of interest, and also in order that the surface elements scanned by the infrared camera present themselves to the camera substantially equally to avoid heat-image distortion. Such equipment is not employed where spatial problems prevent such a set-up. For example, in a coking chamber, the temperature in the interior of the chamber is extremely high, the surface area of the interior side walls very large, and the distance from which the camera could be perpendicularly spaced from the side wall extremely small, making the use of such a technique impossible.
Therefore, in applications such as this, considerable work has been done to develop alternative techniques for ascertaining temperature profiles. Thus, it is known to measure the temperatures of the interior side walls of coking chambers using optical pyrometers inserted through the charging openings at the tops of the coking chambers. However, such pyrometers are basically capable of measuring the temperature of only individual surface points, and therefore cannot readily generate information indicating the temperature profile across the whole, and rather large surface of the side wall; attempts to use such pyrometers to generate a whole temperature profile across the whole side-wall surface are so time-consuming as to be impractical for routine use during routine operation of the coking-oven battery.
Published allowed German Federal Republic patent application DT-AS No. 12 25 143 discloses a method for measuring the temperatures of wall surfaces. This technique involves the use of a radiation detector mounted on a rod. The rod is displaced to cause the radiation detector to travel along and parallel to the wall surface of interest. However, this system is very problematic. If only a single radiation detector is employed, what is ascertained is merely the temperature profile along a narrow line of the large wall surface. Even if one employs a plurality of such detectors spaced perpendicular to the scanning direction, this merely generates such information for a plurality of narrow lines of the large wall surface. Despite the expense, information establishing a temperature profile across the whole surface area of the wall, cannot be practically generated. Also, this type of system is burdened by a great deal of generated misinformation, resulting from temperature differences as between the wall surface and the measuring equipment itself.